how do I reinstall windows defender for windows 10

Hi Lucy,

Welcome to Microsoft community.

• How did you uninstall Windows Defender?

Please follow the below steps and check:

 Step 1: Enable Windows defender from control panel 

1.    Press Windows + X, Click on control panel.

2.    On right top corner click on View and then choose large items.

3.    Now from the list click on Windows Defender and try to enable it. 

If not try to enable it from services. 

Step 2: Enable Windows defender from services.msc. 

1.    Press Windows + R, to open run prompt.

2.    Type services.msc and press enter to open services list.

3.    Under services look from Windows defender service and start the service.

If you face any issue while troubleshooting, please provide the outcome, so that we can work on your issue. 

Hope the information helps, if you have any further queries, feel free to post. We are here to assist you.

Rehards,

Guru Kiran

error 577

windows defender cannot be enabled

because of the above error

not working,the window defender service, service on local computer started and then stopped.some services stop automatically if they are not in use by other services or program.

This did not fix my windows defender, either option.  I get an error code that says something may have changed my setting but it will not let me enable defender.  Any ideas?  Can I reload just the defender portion?

How to swich on microsoft defender in windows 10??